1. Field of the Invention
The present invention relates to a system for and a method of supplying a processing solution, such as a resist solution or a developer, to a substrate, such as a semiconductor wafer or a glass substrate for an LCD, and a processing solution supply control program.
2. Description of the Related Art
Generally, a thin ITO film (indium tin oxide film) or an electrode pattern is formed on a semiconductor wafer or a glass substrate for an LCD (hereinafter, referred to as “wafer”) by photolithography to fabricate a semiconductor device. Photolithography applies a photoresist to a wafer or the like to form a resist film on the wafer, exposes the resist film to light through a mask to form an image of a circuit pattern in the resist film, and processes the exposed resist film to form a circuit pattern in the resist film.
In photolithographic steps, a processing solution supply system is used for supplying the processing solution to the wafer. The processing solution supply system supplies the processing solution by pressure from a tank containing the processing solution or by suction by a pump plated in a supply line.
A processing solution supply system of this type disclosed in JP-A No. 2002-246306 (claims and FIG. 2) includes a plurality of processing solution tanks containing processing solutions, supply lines provided with selector valves and connecting the processing solution tanks to processing solution discharge nozzles, a temporary storage tank for temporarily storing the processing solutions from the processing solution tanks, and an exhaust line provided with a liquid surface detector and an air vent mechanism and connected to the temporary storage tank.
This known processing solution supply system can change the empty processing solution tank with another processing solution tank by controlling the selector valve by a controller which receives a detection signal from the liquid surface detector. Thus wafer or the like can be continuously processed.
Another processing liquid supply system disclosed in JP-A No. 2004-128441 (Paragraph No. 007 and FIG. 3) includes an exhaustion sensor capable of sensing the exhaustion of a processing solution tank and placed in a processing solution supply line connected to the processing solution tank instead of placing a liquid surface detector in a temporary storage tank.
It is important for such a processing solution supply system to supply a processing solution in a constant supply condition, such as a condition in which the processing solution is supplied at a constant pressure.
A pressurizing system that pressurizes a processing solution contained in a processing solution tank by a pressurizing means to supply the processing solution by pressure to a processing solution discharge nozzle has a problem that the processing solution cannot be supplied at a constant pressure because the pressure applied to the processing solution decreases as the amount of the processing solution contained in the processing solution tank decreases.
The pressure supply system cannot supply the processing solution while the processing solution tanks are changed. As mentioned in JP-A Nos. 2002-246306 and 2004-128441, such a problem may be solved by an arrangement that connects a plurality of processing solution tanks through selector valves to a temporary storage tank. This arrangement, however, needs pressure lines for connecting the processing solution tanks to a pressurizing means, and selector means placed in the pressure lines. Consequently, the processing solution supply system provided with such an arrangement has complicated, large construction.